694 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



RELATION TO LAKE WAKREN. 



After forming the Batavia moraine the ice sheet apparently withdrew 

 from the Corniferous escarpment sufficiently to allow the waters of the 

 Genesee glacial lake to enter Lake Warren and take the level of that lake. 

 This blending of the lakes in all probability occurred while the drumlins 

 and their attendant morainic phenomena were being produced, and the 

 connecting portion of the beach of Lake Warren would date from this 

 time. Possibly the lake waters were barred out or were of little effect for 

 a considerable part of the time that the drumlins were form ng, for drumlins 

 were apparently submarginal rather than terminal accumulations of the 

 ice sheet; but the southern portion of the belt, with its morainic knolls 

 and pitted gravel plains, seems to liave been nearly coincident with the ice 

 margin for at least part of the time. 



It is a matter of much significance that these pitted gravel plains 

 appear at levels far below the level of Lake Wan-en and in positions 

 where it would seem probable that the lake had free access to the ice 

 margin. Those near Oakfield are fully 100 feet below the level of the 

 neighboring part of the beach of Lake Warren, while those along the 

 border of Aliens Creek are 150 to 250 feet or more below the beach. 

 There is a gravel plain just west of Scottsville on the north side of Aliens 

 Creek which stands between the 580 and 600 foot contours, or about 275 

 feet below the beach of Lake Warren. This has been extensively opened 

 for gravel in a direction favorable for sliowing the mode of formation, there 

 being a pit about one-fourth of a mile long extending from north to south 

 across the gravel plain. The bedding shows that it was built by a stream 

 moving southward away from the ice sheet but up the Genesee Valley. 

 The beds were built out from nortli to south in the form of a delta, the 

 topset and foreset beds being well exposed. The dip of the foreset beds 

 is most abrupt in the middle part of the pit, being 25° to 30° below the 

 horizontal. With the advance of the delta southward the angle of dip 

 decreases to 10° or less. The material is a sandy gravel with many stones 

 2 or 3 inches in diameter. It is, on the whole, finer and less distinctly 

 assorted than in the outwash gravels formed in situations where the water 

 had free escape. If Lake Warren still persisted the material contained in 

 this delta and other gravelly deposits along the southern border of the 

 drumlin belt seems likely to have been forced out by hydrostatic pressure 

 from the edg-e of the ice sheet into the bordering- lake. 



